WaveShop - Open source audio editor
MilkyTracker - MilkyTracker is an open source, multi-platform music application for creating .MOD and .
TwistedWave - TwistedWave is one of the unique audio editors that allow you to edit your music file online without any installation.
OpenMPT - OpenMPT is a popular tracker software for Windows.
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
FamiStudio - FamiStudio is very simple music editor for the Nintendo Entertainment System or Famicom. It is designed to be easier to use than FamiTracker, but its feature set is also much more limited.